Clear plastic packaging is usually made of low density polythene, and is usually called ‘clear poly bags’. They are designed for a multitude of plastic packaging needs, most commonly for protecting items from dust and moisture. When they are used for food, they can be heat-sealed to retain freshness. Common uses are for protecting furniture, artworks, clothing, bedding, items in transit, electronic parts, freezer storage, and for outdoor protection against ultraviolet degradation.
The process for making polythene film is called Blown Film Extrusion. Resin, which is made of small plastic pellets, is melted until molten and then pressed (extruded) through a circular die gap to form a continuous tube of plastic. While still molten, the tube is pinched off at one end then blown and stretch to the size required for the finished product. The blown-up bubble is then drawn up and cooled before being flattened out and wound onto a roll. This clear plastic packaging process can be used to make any thickness of film.
Individual clear plastic bags are made by heat-sealing and cutting rolls of film. The rolls of tubing are fed through a machine that cycles to seal the material and then cut off to make a single bag. Machine cycle speeds can product up to 70,000 bags an hour.
The mini clear plastic bag is tiny. From 4.5 to 10 centimetres wide, it is used for holding small items such as screws, bolts, and even sweets. The extra large bags measure up to 122 centimetres wide.
The bubble wrap bag is an innovation developed accidentally by two engineers in New Jersey, U.S.A. They were developing a plastic wallpaper with a paper backing. It didn’t sell too well, until they realised it had an ideal cushioning material for clear plastic packaging. It was lightweight, water-resistant, and re-usable. Bubble wrap is manufactured in the same way as a plastic bag, but the resin goes into an extruder with a screw inside. As the screw is turned and the resin melts, the plastic is squeezed out into two stacked sheets of clear film. One layer has holes punched in it and the other web of film is sucked into the holes that form the bubbles. The second layer of film is laminated over the first layer, and when the two films are joined, they stick together and trap air in the bubbles. The bubbles range in size from 6 to 25 millimetres in diameter up to 4 millimetres in height.
While it sounds easy, polyethylene is, in fact, a porous material, which means that air can easily leak through the pores. So, the bubbles have to be sealed during extrusion.
Bubble wrap is the perfect clear plastic packaging for transporting goods. It is lightweight, transparent, moisture-resistant, protects against abrasion, has good insulation, is strong and elastic, and is easy to trim. It protects goods during transit and is available in different types and sizes for storing goods.
Adhesive bubble wrap sticks to anything. Cohesive bubble wrap sticks to itself. Antistatic bubble wrap is used to protect electronic components that may be damaged from static.